1. Field of the Invention
The present invention relates to an ink jet recording apparatus which comprises an ink supply system for replenishing a subtank with an ink from a main tank.
2. Description of the Related Art
As an ink jet recording apparatus, there has conventionally been used an apparatus of a so-called serial scanning type in which a recording head as recording means and an ink tank as an ink container are replaceably mounted on a carriage movable in a main scanning direction. The ink jet recording apparatus of this type is constituted in such a manner that images are sequentially recorded on a recording medium by repeating main scanning of the carriage on which the recording head and the ink tank are mounted, and subscanning feeding of the recording medium such as a recording sheet.
If consideration is given to realization of a compact ink jet recording apparatus specialized for a digital camera (in this case, a maximum recording width is about equal to that of A6, and a so-called L size or the like of a photograph can be recorded), or a more compact ink jet printer suited to personal digital assistants (PDA), a camera or the like (in this case, a maximum recording width is about equal to that of a name card or a card size) by using such a recording system of a serial scanning type, a carriage is made compact, and thus a capacity (volume) of an ink tank mounted thereon must be greatly reduced. However, if the capacity of the ink tank on the carriage is extremely small, there is a possibility that replacement of the ink tank will become frequent, or the ink tank will have to be replaced in the middle of a recording operation.
In order to solve the aforementioned problem, Japanese Patent Application Laid-Open No. 2000-334982 or the like discloses an ink supply mechanism (referred to as a pit-in ink supply mechanism, hereinafter) for replenishing an ink containing portion (referred to as a subtank, hereinafter) on a carriage with an ink from an ink containing portion (referred to as a main tank, hereinafter) disposed on an apparatus main body side separately from the carriage at proper timing each time the carriage moves to a predetermined standby position. A capacity of the main tank is normally much larger than that of the subtank.
The pit-in ink supply mechanism is constituted in such a manner that, for example, each time recording is carried out on one recording medium, the carriage is moved to the predetermined standby position to connect the subtank on the carriage to the main tank by a joint member, and an ink is supplied from the main tank to the subtank in this connected state. In this case, since a constitution is employed to enable holding (storing) of an ink of a maximum amount likely to be consumed at least on one recording medium in the subtank, the aforementioned problem of the frequent tank replacement caused by the very small ink capacity of the subtank on the carriage can be solved. Here, the subtank is designed to be small in volume for miniaturization of the apparatus main body, which is large enough to contain an ink of an amount necessary for image recording of one recoding medium of a predetermined size assumed by the used recording apparatus.
For example, a size of the recording medium is set to 4″×6″ (4 inches×6 inches) at the maximum, and a so-called L size used in photography, and a size of a postcard or the like can be contained. If resolution of a main scanning direction is 2400 dpi, and resolution of a subscanning direction is 1200 dpi, then ink drops of about 7×107 dots are discharged. In this case, if a volume of an ink drop (one droplet) discharged from a recording head is, e.g., 3 pl, a maximum ink amount necessary for recording becomes about 0.2 ml. Accordingly, by setting an ink amount used for suction recovery or pre-discharging frequently used in the normal ink jet recording apparatus to 0.05 ml, and further including a margin, a volume of the subtank can be designed to be a size large enough to contain an ink of, e.g., 0.3 ml.
The Japanese Patent Application Laid-Open No. 2000-334982 describes an ink jet recording apparatus which comprises the ink supply system (pit-in ink supply system) for replenishing the subtank on the carriage with an ink from the main tank at proper timing.
Additionally, in Japanese Patent Application Laid-Open No. 11-138851 (U.S. Pat. No. 6,540,321), there is a description to the effect that a re-soluble liquid is passed through an ink flow path to enable recovery if ink solidification (fixing) occurs in the ink flow path when a pigmented ink is used.
Furthermore, in Japanese Registered Patent No. 3180401 (U.S. Pat. No. 5,382,969), there is a description to the effect that ink consumption is blocked (work is discontinued while the ink remains) at a point of time when an ink residual amount in the subtank drops below a prescribed amount.